I tried one once and it doesn't work very well. When you are coasting, the tight part of the chain is on the bottom and the top goes slack. So when you give it gas, the chain slopps around a lot feeding into the engine sprocket and it can jam in there. Not good. This caused my back wheel to lock up at about 30mph going down a hill. I didn't crash or anything but it could have been worse.

Now that I think about it, if you were using the HD wheel with a freewheel in the back it shouldn't cause any problems.

I don't remember where I got that tensioner, but it was only about $30.

I have tried the spring tensioner set up on 2 different bikes. and it is a good way to trash a chain and even possibly wreck a wheel, I would tell you to stay away from the spring set up, I built a tensioner and used a skateboard wheel for the guide roller, it works great and I never lost another chain or had any problems since, I will never use a spring tensioner on a bike again.